The present invention relates to a repairable ballast for fluorescent lights, but offers, in fact, wider possibilities as to application and use.
The ballast element for fluorescent lighting includes usually a ballast coil proper, a step-up transformer, a power factor capacitor or capacitors, and, possibly, other auxiliary elements, all mounted and assembled in a module-type, unitary configuration. Such ballast elements are, of course, used wherever fluorescent lamps are being used. In most instances (i.e., household use), special precautions are not needed. The situation is different for lighting of vehicles and aircraft. Circuit integrity requires extensive shock-proofing and, of course, consistent heat dissipation. Accordingly, a ballast, as defined and to be used in an aircraft lighting system, has been potted. This practice has proven to be consistently successful. The circuit elements are well protected; they will not vibrate, so that circuit connections do not break. Also, heat dissipation is quite adequate through the potting material. However, potting adds considerable weight; and weight is always a problem in aircraft equipment. Moreover, a potted ballast is not repairable. This is, of course, true generally; a circuit element or assembly, once potted, is no longer accessible. Removal of the potting is inherently destructive. Thus, a potted ballast which has failed because of a defect of one element or even because of one connection has to be replaced in its entirety; it is not repairable. Repairability requires access, but ease of access must not compromise shock-proofing. Apparently then, shock-proofing and repairability are opposing constraints; they appear to be mutually exclusive.